package org.example.utils;

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.JwtBuilder;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;

import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;
import java.util.Date;
import java.util.UUID;

public class JwtUtil {

    //有效期为
    public static final Long JWT_TTL = 60*60*1000L; //一个小时
    //设置密钥明文
    public static final String JWT_KEY = "hzj";

    public static String getUUID(){
        String token = UUID.randomUUID().toString().replaceAll("-","");
        return token;
    }

    /**
     * 生成jwt
     * @param subject token中要存放的数据（json格式）
     * @return
     */
    public static String createJWT(String subject){
        JwtBuilder builder = getJwtBuilder(subject,null,getUUID()); //设置过期时间
        return builder.compact();
    }

    /**
     * 生成jwt
     * @param subject token中要存放的数据（json格式）
     * @param ttlMillis token超时时间
     * @return
     */
    public static String createJWT(String subject,Long ttlMillis){
        JwtBuilder builder = getJwtBuilder(subject,ttlMillis,getUUID()); //设置过期时间
        return builder.compact();
    }

    private static JwtBuilder getJwtBuilder(String subject,Long ttlMillis,String uuid){
        SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.HS256;
        SecretKey secretKey = generalkey();
        long nowMillis = System.currentTimeMillis();
        Date now = new Date(nowMillis);
        if(ttlMillis==null){
            ttlMillis=JwtUtil.JWT_TTL;
        }
        long expMillis = nowMillis + ttlMillis;
        Date expDate = new Date(expMillis);
        return Jwts.builder()
                .setId(uuid) //唯一的Id
                .setSubject(subject) //主题 可以是Json数据
                .setIssuer("hzj") //签发者
                .setIssuedAt(now) //签发时间
                .signWith(signatureAlgorithm,secretKey) //使用HS256对称加密算法签名，第二个参数为密钥
                .setExpiration(expDate);
    }

    /**
     * 创建token
     * @param id
     * @param subject
     * @param ttlMillis
     * @return
     */
    public static String createJWT(String id,String subject,Long ttlMillis){
        JwtBuilder builder = getJwtBuilder(subject,ttlMillis,id);//设置过期时间
        return builder.compact();
    }

    public static void main(String[] args) throws Exception{
        Claims claims = parseJWT("eyJhbGciOiJIUzI1NiJ9.eyJqdGkiOiIxOWYxZGZlZTkwNGQ0ODdlOTA5Zjg3ZmQ3MjBlYjI0MCIsInN1YiI6IjEiLCJpc3MiOiJoemoiLCJpYXQiOjE3MTg5NTQ0ODAsImV4cCI6MTcxODk1ODA4MH0.65W3eK-fiRm8HsYJI6hhZUXqecBfCdw68YrxB1HAwCY");
        String subject = claims.getSubject();
        System.out.println(subject);
    }

    /**
     * 生成加密后的密钥secretkey
     * @return
     */
    public static SecretKey generalkey(){
        byte[] encodeedkey = Base64.getDecoder().decode(JwtUtil.JWT_KEY);
        SecretKey key = new SecretKeySpec(encodeedkey,0,encodeedkey.length,"AES");
        return key;
    }

    /**
     * 解析
     * @param jwt
     * @return
     * @throws Exception
     */
    public static Claims parseJWT(String jwt) throws Exception{
        SecretKey secretKey = generalkey();
        return Jwts.parser()
                .setSigningKey(secretKey)
                .parseClaimsJws(jwt)
                .getBody();
    }
}
